micromobility - Ebikes, scooters, longboards: Whatever floats your goat, this is micromobility
Ebikes, bicycles, scooters, skateboards, longboards, eboards, motorcycles, skates, unicycles: Whatever floats your goat, this is all things micromobility!
"Transportation using lightweight vehicles such as bicycles or scooters, especially electric ones that may be borrowed as part of a self-service rental program in which people rent vehicles for short-term use within a town or city.
micromobility is seen as a potential solution to moving people more efficiently around cities"
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You're right, but I think there are some other benefits to doing away with the chain. I have an E-mountain bike and between chain stretch, chain damage, and mud I go through 2 chains per season plus a couple trail-side repairs. Also, no chain means you can optimize pedal speed/torque for each individual rider, and keep it in the ideal range all the time regardless of bike speed. Essentially it offers a much wider power band than gears and a chain. You could also optimize crank length for clearance instead of torque. The front chainring is also a big point of contact on mountain bikes, removing that could improve clearance with the right design. I'd also be interested in the regenerative braking - if I go on an Enduro ride I'm cooking my brakes on much of the downhill, regen could save those and recharge the battery at the same time. Maybe regen could even lead to a smaller battery and save some weight.
Sure there are disadvantages - weight, complexity, efficiency, probably others too. I think with time those will improve though and this just might be a viable setup for certain use cases.
I do see your points, where the chain itself is the cause of inconvenience or failure scenarios. Since the conventional bicycle is almost the textbook definition of minimal design, there are -- and will always ever be -- tradeoffs to make, and I concede that efficiency isn't always everyone's top priority for their bicycle.
While I cannot discount that this chainless system would ameliorate the situations you described, I can offer some alternatives which can or already do exist today, that could probably be explored and improved over what this chainless system delivers.
The older style of shaft drives in lieu of a chain could be maintenance free, and damage resistant. Efficiency is lower, and roadside repair is much harder, but efficiency is already lowered when in messy terrain, and if it's fully sealed, it might last a very long time anyway. Reviving this concept is something I could reasonably see.
Having discrete gear ratios will indeed always be a limiting factor when dealing with variable speeds, but there already exists a CVT (continuous variable transmission) for bicycles, where torque and speed can be traded in non-stairstep fashion. That said, no one makes a CVT with a built in ebike motor..... yet.
I think I understand what you mean here, in that cranks today draw a larger circle to accommodate human physiology, but that also increases the risk of a pedal striking the road, or rocks adjacent to a trail. But I don't see how this chainless system can change the crank circle diameter on-the-fly. And I don't envision people wanting that very often, unless they want small diameter on trails and then want to bike home on the roads by switching to a large diameter.
I think this already exists for ebikes: https://radpowerbikes.zendesk.com/hc/en-us/articles/360045171734-Riding-Rad-with-regenerative-braking
I want to be clear: I'm not trying to shoot down the idea of chainless systems out-of-hand. But rather, these other solutions to your scenarios are more grounded in existing technology, or are waiting to be further refined before mass adoption, and likely will cost a lot less.